JP2013222800A - Nitride semiconductor device and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride semiconductor device and a manufacturing method of the same, which can reduce contact resistance between a nitride semiconductor layer and an ohmic electrode.SOLUTION: In a GaN HFET, a 2DEG layer 3 is formed near heterointerface between an undoped GaN layer 1 and an undoped AlGaN layer 2, and ohmic electrodes (source electrode 11, drain electrode 12) composed of a TiAl material are formed in recesses 106, 109 which pierce the 2DEG layer 3 by sequentially sputtering a Ti film 107, Al and TiN and performing annealing at 400°C-550°C. A full width at half maximum (FWHM) of a (002) plane rocking curve obtained by X-ray diffraction of the Ti film 107 which is formed when the source electrode 11 and the drain electrode 12 are manufactured is set at 7° and over.

Description

  The present invention relates to a nitride semiconductor device and a method for manufacturing the same.

  Conventionally, as a nitride semiconductor device, an AlGaN layer is formed on a GaN layer, and Ti and Al are vapor-deposited in this order in a recess extending from the AlGaN layer to the GaN layer, and heat-treated at 700 ° C. to form an ohmic electrode. Is disclosed in Patent Document 1 (Japanese Patent No. 4333352).

  However, when the inventor actually conducted an experiment on the nitride semiconductor device to form an ohmic electrode, the contact resistance of the ohmic electrode was high, and a sufficiently low contact resistance could not be obtained.

Japanese Patent No. 4333352

  SUMMARY OF THE INVENTION An object of the present invention is to provide a nitride semiconductor device that can reduce the contact resistance between the nitride semiconductor layer and the ohmic electrode, and a method for manufacturing the same.

  In the present invention, in the course of various experiments by the inventor, an ohmic electrode made of a TiAl-based material of a nitride semiconductor device is unexpectedly expected to have a reduced contact resistance when formed by breaking the crystallinity of Ti. It was created based on the knowledge of

That is, the nitride semiconductor device of the first invention is
A substrate,
A nitride semiconductor multilayer body formed on the substrate and having a heterointerface;
An ohmic electrode made of a TiAl-based material formed at least partially on the nitride semiconductor multilayer body or in the nitride semiconductor multilayer body,
The nitride semiconductor laminate is
A first nitride semiconductor layer formed on the substrate;
A second nitride semiconductor layer formed on the first nitride semiconductor layer and forming a heterointerface with the first nitride semiconductor layer;
The ohmic electrode made of the TiAl-based material is
A Ti film having a half-width of a rocking curve of (002) plane by X-ray diffraction of 7 ° or more is formed on the nitride semiconductor multilayer body, an Al film is laminated on the Ti film, and the Al film is laminated on the Al film. It is characterized by being manufactured by heat treatment so that Ti of the Ti film diffuses.

  According to the nitride semiconductor device of the first aspect of the invention, the Ti film formed when the ohmic electrode made of the TiAl-based material has a half width of the rocking curve of the (002) plane by X-ray diffraction is 7 °. By the above, a low contact resistance (for example, 2 Ωmm or less) can be obtained.

In one embodiment of the nitride semiconductor device, the nitride semiconductor stack is
Having a recess that penetrates the second nitride semiconductor layer and reaches the two-dimensional electron gas layer near the heterointerface;
At least a part of the ohmic electrode is embedded in the recess.

  According to this embodiment, in the nitride semiconductor device having a recess structure, the contact resistance between the two-dimensional electron gas layer and the ohmic electrode in the vicinity of the heterointerface between the first nitride semiconductor layer and the second nitride semiconductor layer is reduced. Can be reduced.

A method for manufacturing a nitride semiconductor device according to the second aspect of the invention includes
First and second nitride semiconductor layers are sequentially formed on a substrate to have a heterointerface by the first and second nitride semiconductor layers, and a two-dimensional electron gas layer is formed in the vicinity of the heterointerface. So as to form a nitride semiconductor stack,
On the nitride semiconductor laminate, Ti is sputtered at a temperature of 50 ° C. or less to form a Ti film having a half-width of a rocking curve of (002) plane by X-ray diffraction of 7 ° or more, and the Ti film Laminating an Al film on top to form a Ti / Al layer,
The Ti / Al layer is heat-treated so that Ti of the Ti film diffuses into the Al film to form an ohmic electrode made of a TiAl-based material.

  According to the second aspect of the present invention, Ti is sputtered at a temperature of 50 ° C. or lower to form a Ti film having a half-width of a rocking curve of (002) plane by X-ray diffraction of 7 ° or more. The Ti / Al layer is formed by laminating an Al film thereon to form an ohmic electrode by the heat treatment. Thereby, an ohmic electrode having a low contact resistance (for example, 2 Ωmm or less) can be obtained.

A method for manufacturing a nitride semiconductor device according to a third aspect of the invention includes
First and second nitride semiconductor layers are sequentially formed on a substrate to have a heterointerface by the first and second nitride semiconductor layers, and a two-dimensional electron gas layer is formed in the vicinity of the heterointerface. So as to form a nitride semiconductor stack,
After flowing oxygen into the sputter chamber, Ti is sputtered on the nitride semiconductor laminate to form a Ti film having a half-width of the rocking curve of the (002) plane by X-ray diffraction of 7 ° or more. Sputter an Al film on the Ti film to form a Ti / Al layer,
The Ti / Al layer is heat-treated so that Ti of the Ti film diffuses into the Al film to form an ohmic electrode made of a TiAl-based material.

  According to the third aspect of the present invention, after flowing oxygen into the chamber, Ti is sputtered on the nitride semiconductor laminate, and the half width of the rocking curve of the (002) plane by X-ray diffraction is 7 ° or more. A Ti film is formed, Al is laminated on the Ti film, and the Ti / Al layer is formed as an ohmic electrode by the heat treatment. Thereby, an ohmic electrode having a low contact resistance (for example, 2 Ωmm or less) can be obtained.

  In one embodiment of the method for manufacturing a nitride semiconductor device, the Ti / Al layer is heat-treated at 400 ° C. or more and 550 ° C. or less to form an ohmic electrode made of the TiAl-based material.

  According to this embodiment, an ohmic electrode having a low contact resistance (for example, 2 Ωmm or less) can be obtained by heat treatment at a low temperature of 400 ° C. to 550 ° C., so that adverse effects on the semiconductor interface and the element itself can be avoided, The reliability and performance of the element can be improved.

  As an example, current collapse can be prevented from deteriorating due to nitrogen depletion from the nitride semiconductor layer. Here, “current collapse” is a phenomenon in which the on-resistance of a transistor in a high voltage operation becomes higher than the on-resistance of the transistor in a low voltage operation.

According to another embodiment of the method of manufacturing a nitride semiconductor device, the two-dimensional electron gas layer in the vicinity of the heterointerface passes through the second nitride semiconductor layer by etching after forming the nitride semiconductor stacked body. Forming a recess that reaches
The ohmic electrode is formed so as to be at least partially embedded in the recess of the nitride semiconductor multilayer body.

  According to this embodiment, in the nitride semiconductor device having a recess structure, the contact resistance between the two-dimensional electron gas layer near the heterointerface and the ohmic electrode can be reduced.

  According to the nitride semiconductor device of the present invention, the Ti film formed when producing an ohmic electrode made of a TiAl-based material has a half width of a rocking curve of the (002) plane by X-ray diffraction of 7 ° or more. Thus, a low contact resistance (for example, 2 Ωmm or less) can be obtained.

It is sectional drawing of the nitride semiconductor device of embodiment of this invention. It is process sectional drawing for demonstrating the manufacturing method of the said nitride semiconductor device. FIG. 3 is a process cross-sectional view subsequent to FIG. 2. FIG. 4 is a process cross-sectional view subsequent to FIG. 3. FIG. 5 is a process cross-sectional view subsequent to FIG. 4. FIG. 6 is a process cross-sectional view subsequent to FIG. 5. 4 is a graph showing a relationship between a half-value width of a rocking curve of a (002) plane of a Ti film laminated on a nitride semiconductor laminated body and contact resistance of an ohmic electrode. It is a graph which shows the relationship between the film-forming temperature of Ti film | membrane, and the half value width of the rocking curve of the (002) plane of the said Ti film | membrane. 6 is a graph showing the relationship between the flow rate of (oxygen + nitrogen) flowing in a chamber before sputtering of a Ti film and the half width of the rocking curve of the (002) plane of the Ti film.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 shows a cross-sectional view of a nitride semiconductor device according to a first embodiment of the present invention, which is a GaN-based HFET (Hetero-junction Field Effect Transistor).

  As shown in FIG. 1, the semiconductor device includes an undoped AlGaN buffer layer 15, an undoped GaN layer 1 as an example of a first nitride semiconductor layer, and an example of a second nitride semiconductor layer on a Si substrate 10. As a result, a nitride semiconductor stacked body 20 composed of the undoped AlGaN layer 2 is formed. A 2DEG (two-dimensional electron gas) layer 3 is generated in the vicinity of the heterointerface between the undoped GaN layer 1 and the undoped AlGaN layer 2.

  In place of the GaN layer 1, an AlGaN layer having a smaller band gap than the AlGaN layer 2 may be used. Further, a layer having a thickness of about 1 nm made of GaN, for example, may be provided on the AlGaN layer 2 as a cap layer.

  Further, the source electrode 11 and the drain electrode 12 are formed in a recess 106 and a recess 109 that penetrate the AlGaN layer 2 and the 2DEG layer 3 to reach the GaN layer 1 and are spaced from each other. Further, a gate electrode 13 is formed on the AlGaN layer 2 between the source electrode 11 and the drain electrode 12 and on the source electrode 11 side. The source electrode 11 and the drain electrode 12 are ohmic electrodes, and the gate electrode 13 is a Schottky electrode. The source electrode 11, the drain electrode 12, the gate electrode 13, and the active regions of the GaN layer 1 and the AlGaN layer 2 on which the source electrode 11, the drain electrode 12, and the gate electrode 13 are formed constitute an HFET.

  Here, the active region is a carrier between the source electrode 11 and the drain electrode 12 due to a voltage applied to the gate electrode 13 disposed between the source electrode 11 and the drain electrode 12 on the AlGaN layer 2. Is a region of the nitride semiconductor stacked body 20 (GaN layer 1, AlGaN layer 2) through which flows.

An insulating film 30 made of SiO ₂ is formed on the AlGaN layer 2 excluding the region where the source electrode 11, the drain electrode 12, and the gate electrode 13 are formed in order to protect the AlGaN layer 2. An interlayer insulating film 40 made of polyimide is formed on the Si substrate 10 on which the source electrode 11, the drain electrode 12, and the gate electrode 13 are formed. In FIG. 1, reference numeral 41 denotes a via as a contact portion, and 42 denotes a drain electrode pad. The material of the insulating film 30 is not limited to SiO ₂ , and SiN, Al ₂ O ₃ or the like may be used. In particular, the insulating film preferably has a multilayer structure of a SiN film having a stoichiometric collapse on the surface of the semiconductor layer to suppress collapse and a SiO ₂ or SiN film structure for surface protection. The interlayer insulating film 40 is not limited to polyimide, but is made of an insulating material such as SiO ₂ film manufactured by p-CVD (plasma CVD), SOG (Spin On Glass), or BPSG (boron / phosphorus / silicate / glass). It may be used.

  In the nitride semiconductor device having the above configuration, a channel is formed by the two-dimensional electron gas layer (2DEG layer) 3 generated in the vicinity of the heterointerface between the GaN layer 1 and the AlGaN layer 2, and a voltage is applied to the gate electrode 13 through this channel. Thus, the HFET having the source electrode 11, the drain electrode 12, and the gate electrode 13 is turned on / off. In the HFET, when a negative voltage is applied to the gate electrode 13, a depletion layer is formed in the GaN layer 1 below the gate electrode 13, and the HFET is turned off. On the other hand, when the voltage of the gate electrode 13 is zero, the HFET 13 is a normally-on type transistor in which the depletion layer disappears in the lower GaN layer 1 and is turned on.

  Next, a method for manufacturing the nitride semiconductor device will be described with reference to FIGS. 2 to 6, the Si substrate and the undoped AlGaN buffer layer are not shown in order to make the drawings easy to see, and the sizes and intervals of the source electrode and the drain electrode are changed.

  First, as shown in FIG. 2, an undoped AlGaN buffer layer (not shown), undoped GaN are formed on a Si substrate (not shown) using MOCVD (Metal Organic Chemical Vapor Deposition). A layer 101 and an undoped AlGaN layer 102 are formed in this order. The thickness of the undoped GaN layer 101 is, for example, 1 μm, and the thickness of the undoped AlGaN layer 102 is, for example, 30 nm. The GaN layer 101 and the AlGaN layer 102 constitute a nitride semiconductor layer 120.

Next, an insulating film 130 (for example, SiO ₂ ) is formed with a thickness of 200 nm on the AlGaN layer 102 by, for example, a plasma CVD (Chemical Vapor Deposition) method. In FIG. 2, reference numeral 103 denotes a two-dimensional electron gas (2DEG) layer formed in the vicinity of the heterointerface between the GaN layer 101 and the AlGaN layer 102.

  Next, after applying and patterning a photoresist on the insulating film 130, a portion where an ohmic electrode is to be formed is removed by dry etching, as shown in FIG. 3, and the GaN layer penetrates the AlGaN layer 102. Recesses 106 and 109 reaching part of the upper side of 101 are formed. The depth of the recesses 106 and 109 may be equal to or greater than the depth from the surface of the AlGaN layer 102 to the 2DEG layer 103, for example, 50 nm. Then, after the dry etching, annealing is performed at 500 to 850 ° C., for example.

  Next, as shown in FIG. 4, a Ti film 107 is formed on the insulating film 130 and in the recesses 106 and 109 by sputtering. The Ti film 107 is formed by sputtering at a low temperature of 50 ° C. or lower. Thereby, the Ti film 107 having a half-value width of the rocking curve of the (002) plane by X-ray diffraction of 7 ° or more is formed. In addition, the lower limit of the sputtering temperature of the Ti film can be set to room temperature (for example, 20 ° C.) as an example.

  Next, Al / TiN is sputtered in the order of Al and TiN on the insulating film 130 and the Ti film 107 formed on the recesses 106 and 109, and an Al / TiN layer in which a TiN film is laminated on the Al film is formed as a Ti film. Laminate on 107. This sputtering temperature is performed at 50 ° C. to 200 ° C., for example. Thereby, as shown in FIG. 5, a laminated metal film 108 to be an ohmic electrode is formed. Here, the TiN layer is a cap layer for protecting the Ti / Al layer from a later step.

  Next, as shown in FIG. 6, patterns of ohmic electrodes 111 and 112 are formed by using normal photolithography and dry etching.

  An ohmic contact is obtained between the 2DEG layer 103 and the ohmic electrodes 111 and 112 by annealing the substrate on which the ohmic electrodes 111 and 112 are formed at, for example, 400 ° C. or more and 550 ° C. or less for 10 minutes or more. In this case, the contact resistance of the ohmic electrodes 111 and 112 can be greatly reduced as compared with the case where annealing is performed at a high temperature exceeding 550 ° C. In addition, by annealing at a low temperature of 400 ° C. or higher and 550 ° C. or lower, diffusion of the electrode metal into the insulating film 130 can be suppressed, and the characteristics of the insulating film 130 are not adversely affected. In addition, the low temperature annealing can prevent deterioration of current collapse and characteristic fluctuation due to nitrogen desorption from the GaN layer 101. Note that “current collapse” is a phenomenon in which the on-resistance of a transistor in a high-voltage operation becomes higher than the on-resistance of the transistor in a low-voltage operation.

  Here, the annealing time is set to 10 minutes or longer. However, the annealing time may be set to a time during which Ti sufficiently diffuses into Al.

  The ohmic electrodes 111 and 112 become the source electrode 11 and the drain electrode 12, and a gate electrode made of TiN or WN is formed between the ohmic electrodes 111 and 112 in a later step.

  In the course of various experiments conducted on a GaN-based HFET, which is one of the nitride semiconductor devices, the present inventors have reduced contact resistance when the Ti crystallinity is broken in an ohmic electrode made of a TiAl-based material. I got an unexpected finding that

  That is, according to this embodiment, the half width of the rocking curve of the (002) plane by X-ray diffraction of the Ti film 107 formed when the ohmic electrodes 111 and 112 made of the TiAl-based material are 7 ° or more. As a result, a low contact resistance (as an example, 2 Ωmm or less) can be obtained.

  In particular, in a semiconductor device using a material that can reduce the on-resistance such as a GaN device, the ratio of the contact resistance to the on-resistance is relatively high, so that it is very possible to reduce the contact resistance to a low value of 2 Ωmm or less. As a product that can be driven at a large current and is suitable for high-temperature operation, it has commercial value in terms of performance and cost.

  FIG. 7 is a graph showing the relationship between the half-value width of the rocking curve of the (002) plane of the Ti film stacked in the recesses 106 and 109 of the nitride semiconductor multilayer body 20 and the contact resistance of the ohmic electrode. As described above, the ohmic electrode is formed by sputtering Al and TiN in the order of Al and TiN and annealing (400 to 550 ° C.) on the Ti film. As shown in FIG. 7, when the half width of the rocking curve on the (002) plane of the Ti film is 7 ° or more (that is, the crystallinity of Ti is low), the contact resistance is reduced to a low value of 2 Ωmm or less. Can be reduced. On the other hand, when the half width of the rocking curve of the (002) plane of the Ti film is less than 7 ° (that is, the crystallinity of Ti is high), the contact resistance increases rapidly.

  FIG. 8 is a graph showing the relationship between the film formation temperature of the Ti film by sputtering and the half width FWHM (°) of the rocking curve of the (002) plane of the Ti film by X-ray diffraction. As shown in FIG. 8, by setting the Ti film formation temperature to 50 ° or less, the half width FWHM (°) of the rocking curve of the (002) plane of the Ti film after the film formation by sputtering is 7 °. That's it. On the other hand, when the Ti deposition temperature exceeds 50 ° C., the full width at half maximum FWHM (°) of the rocking curve of the (002) plane of the Ti film suddenly decreases from 7 °.

  Thus, by setting the temperature of Ti film formation by sputtering to 50 ° C. or less, the crystallinity of Ti is lowered, and the FWHM of the rocking curve of the (002) plane of the Ti film after film formation is FWHM. (°) can be set to 7 ° or more, and the contact resistance of the ohmic electrodes 111 and 112 can be reduced to a low value of 2 Ωmm or less.

(Second embodiment)
Next explained is a method for manufacturing a nitride semiconductor device as a second embodiment of the invention. The second embodiment is different from the nitride semiconductor device manufacturing method described in the first embodiment only in the point relating to the formation of the Ti film 107. Therefore, in the second embodiment, differences from the method for manufacturing the nitride semiconductor device described in the first embodiment will be mainly described.

  In the manufacturing method of the second embodiment, as described with reference to FIGS. 2 and 3 in the first embodiment, the undoped GaN layer 101 and the undoped AlGaN layer 102 are sequentially formed, and the AlGaN layer 102 is formed. An insulating film 130 is formed thereon, and the recesses 106 and 109 are formed by dry etching.

Next, oxygen gas O ₂ and nitrogen gas N ₂ are flowed into the sputtering chamber at a flow rate of 20 sccm for oxygen gas O ₂ and 80 sccm for nitrogen gas N ₂ for 5 minutes. As shown in FIG. 4, a Ti film 107 is formed on the insulating film 130 and in the concave portions 106 and 109. Thereby, the Ti film 107 having a half-value width of the rocking curve of the (002) plane by X-ray diffraction of 7 ° or more is formed.

  Next, in the same manner as described with reference to FIGS. 5 and 6 in the first embodiment, Al / TiN is laminated on the Ti film 107 by sputtering to form the laminated metal film 108 to be an ohmic electrode. The pattern of the ohmic electrodes 111 and 112 is formed by dry etching. Furthermore, an ohmic contact is obtained between the 2DEG layer 103 and the ohmic electrodes 111 and 112 by annealing at 400 ° C. or more and 550 ° C. or less for 10 minutes or more. The sputtering temperature of the Ti film 107 and Al / TiN is set to 50 ° C. to 200 ° C. as an example.

  According to the manufacturing method of the second embodiment, the half width of the rocking curve of the (002) plane by X-ray diffraction of the Ti film 107 formed when the ohmic electrodes 111 and 112 made of the TiAl-based material are manufactured is 7 When it is at least, it is possible to obtain a low contact resistance (for example, 2 Ωmm or less).

FIG. 9 shows the (N ₂ + O ₂ ) purge volume (cc), which is the sum of the volume (cc) of oxygen gas flowing into the sputtering chamber and the volume (cc) of nitrogen gas, on the horizontal axis. It is the graph which took the full width at half maximum FWHM (°) of the rocking curve of the (002) plane of the Ti film on the vertical axis. Referring to FIG. 9, it can be seen that when the (N ₂ + O ₂ ) purge volume (cc) is about 40 cc or more, the full width at half maximum FWHM (°) is 7 ° or more. Here, the ratio of the flow rate of the oxygen gas to the flow rate of the nitrogen gas was set to a quarter. From FIG. 9, it can be seen that the full width at half maximum FWHM (°) is smaller than 7 ° when the (N ₂ + O ₂ ) purge volume (cc) is less than about 40 (cc). Note that the ratio of the flow rate of the oxygen gas to the flow rate of the nitrogen gas is not limited to a quarter, and may be, for example, 10 to 100%.

  That is, as in the manufacturing method of the second embodiment, by flowing oxygen gas into the sputtering chamber before sputtering of the Ti film 107, the half width of the rocking curve of the (002) plane by X-ray diffraction is 7 °. The Ti film 107 as described above can be formed. Then, by laminating Al / TiN on this Ti film 107 and annealing (400 to 550 ° C., 10 minutes), a low contact resistance (for example, 2 Ωmm or less) between the ohmic electrodes 111 and 112 and the 2DEG layer 103 is reduced. Can be achieved.

  According to the nitride semiconductor device manufacturing method of the above embodiment, the insulating film 130, the AlGaN layer 102, and the GaN layer 101 are removed by dry etching to form the recesses 106 and 109. However, the insulating film 130 is wet etched. The recesses 106 and 109 may be formed by removing the AlGaN layer 102 and the GaN layer 101 by dry etching. In the example shown in FIGS. 7 to 9 of the above embodiment, the upper limit of the full width at half maximum of the rocking curve of the (002) plane of the Ti film is about 7.2 °, but the film formation temperature by sputtering (50 ° C. The Ti film having a half-value width of the rocking curve of the (002) plane of 9.0 ° could be formed depending on the setting of the amount of oxygen gas flowing into the sputtering chamber or the following. Also in this case, the contact resistance of the ohmic electrode produced by sputtering Al and TiN on the Ti film in the order of Al and TiN and annealing (400 to 550 ° C.) could be reduced to a low value of 2.0 Ωmm. For example, the Ti film is formed under the following conditions: a film forming temperature of 200 ° C., oxygen gas is supplied to the sputtering chamber at 20 sccm for 2.5 minutes, and then nitrogen gas is supplied at 80 sccm for 2.5 minutes. As a result, the full width at half maximum FWHM of the rocking curve by X-ray diffraction of the (002) plane of the Ti film was 9.0 °, and the contact resistance of the ohmic electrode was 2.0 Ωmm.

  Further, according to the nitride semiconductor device manufacturing method of the above embodiment, Ti / Al / TiN is laminated to form an ohmic electrode. However, the present invention is not limited to this, and TiN may be omitted, and Ti / Al is laminated. Then, Au, Ag, Pt or the like may be laminated thereon.

  In the above embodiment, the nitride semiconductor device using the Si substrate has been described. However, the present invention is not limited to the Si substrate, and a sapphire substrate or an SiC substrate may be used, and a nitride semiconductor layer is formed on the sapphire substrate or the SiC substrate. The nitride semiconductor layer may be grown on a substrate made of a nitride semiconductor, such as by growing an AlGaN layer on a GaN substrate. Further, a buffer layer may be formed between the substrate and the nitride semiconductor layer, or a hetero-improvement layer between the first nitride semiconductor layer and the second nitride semiconductor layer of the nitride semiconductor stacked body. May be formed.

  In the above-described embodiment, the recess structure HFET in which the ohmic electrode reaches the GaN layer has been described. However, the present invention is applied to an HFET in which an ohmic electrode serving as a source electrode and a drain electrode is formed on an undoped AlGaN layer without forming a recess. May be applied. In addition, the nitride semiconductor device of the present invention is not limited to an HFET that uses 2DEG, and the same effect can be obtained even with field effect transistors having other configurations.

  In the above embodiment, a normally-on type HFET has been described. However, the present invention may be applied to a normally-off type nitride semiconductor device. Further, the present invention may be applied not only to a Schottky electrode but also to a field effect transistor having an insulated gate structure. The present invention is not limited to a field effect transistor, and may be applied to an ohmic electrode of a Schottky diode.

The nitride semiconductor of the nitride semiconductor device of the present invention may be any material expressed by Al _x In _y Ga _1-xy N (x ≦ 0, y ≦ 0, 0 ≦ x + y ≦ 1).

  Although specific embodiments of the present invention have been described, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1,101 GaN layer 2,102 AlGaN layer 3,103 2DEG layer 10 Si substrate 11 Source electrode 12 Drain electrode 13 Gate electrode 15 AlGaN buffer layer 20,120 Nitride semiconductor laminated body 30,130 Insulating film 40 Interlayer insulating film 41 Via 42 Drain electrode pad 106, 109 Recess 111, 112 Ohmic electrode

Claims (5)

A substrate,
A nitride semiconductor multilayer body formed on the substrate and having a heterointerface;
An ohmic electrode made of a TiAl-based material formed at least partially on the nitride semiconductor multilayer body or in the nitride semiconductor multilayer body,
The nitride semiconductor laminate is
A first nitride semiconductor layer formed on the substrate;
A second nitride semiconductor layer formed on the first nitride semiconductor layer and forming a heterointerface with the first nitride semiconductor layer;
The ohmic electrode made of the TiAl-based material is
A Ti film having a half-width of a rocking curve of (002) plane by X-ray diffraction of 7 ° or more is formed on the nitride semiconductor multilayer body, an Al film is laminated on the Ti film, and the Al film is laminated on the Al film. A nitride semiconductor device manufactured by heat treatment so that Ti in a Ti film diffuses. The nitride semiconductor device according to claim 1,
The nitride semiconductor laminate is
Having a recess that penetrates the second nitride semiconductor layer and reaches the two-dimensional electron gas layer near the heterointerface;
A nitride semiconductor device, wherein at least part of the ohmic electrode is embedded in the recess. First and second nitride semiconductor layers are sequentially formed on a substrate to have a heterointerface by the first and second nitride semiconductor layers, and a two-dimensional electron gas layer is formed in the vicinity of the heterointerface. So as to form a nitride semiconductor stack,
On the nitride semiconductor laminate, Ti is sputtered at a temperature of 50 ° C. or less to form a Ti film having a half-width of a rocking curve of (002) plane by X-ray diffraction of 7 ° or more, and the Ti film Laminating an Al film on top to form a Ti / Al layer,
A method of manufacturing a nitride semiconductor device, comprising: heat-treating the Ti / Al layer so that Ti of the Ti film diffuses into the Al film to form an ohmic electrode made of a TiAl-based material. First and second nitride semiconductor layers are sequentially formed on a substrate to have a heterointerface by the first and second nitride semiconductor layers, and a two-dimensional electron gas layer is formed in the vicinity of the heterointerface. So as to form a nitride semiconductor stack,
After flowing oxygen into the sputter chamber, Ti is sputtered on the nitride semiconductor laminate to form a Ti film having a half-width of the rocking curve of the (002) plane by X-ray diffraction of 7 ° or more. Laminating an Al film on the Ti film to form a Ti / Al layer,
A method of manufacturing a nitride semiconductor device, comprising: heat-treating the Ti / Al layer so that Ti of the Ti film diffuses into the Al film to form an ohmic electrode made of a TiAl-based material. In the manufacturing method of the nitride semiconductor device according to claim 3 or 4,
After forming the nitride semiconductor stacked body, etching forms a recess that penetrates the second nitride semiconductor layer and reaches the two-dimensional electron gas layer near the heterointerface,
The method of manufacturing a nitride semiconductor device, wherein the ohmic electrode is formed so as to be at least partially embedded in a concave portion of the nitride semiconductor multilayer body.

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